Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

882
FXUS63 KLOT 260813
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
213 AM CST Mon Jan 26 2026

.KEY MESSAGES...

- Cold Weather Advisory in effect this morning for wind chills
  around 20 below.

- Slight chance for light snow northeast of about I-90 tonight.
  Turning blustery Tuesday with a small chance for a few snow
  showers.

- Cold conditions continue through the week with mainly dry
  conditions. Monitoring another potential for lake effect snow
  during the Thursday night - Saturday timeframe.

&&

.DISCUSSION...
Issued at 213 AM CST Mon Jan 26 2026

A sprawling 1040-ish mb arctic high building across the Great
Plains has brought an end to our accumulating snowfall and at
the same time is ushering in a renewed push of cold air.
Temperatures at this hour are wandering down below zero across
interior northern Illinois and into the single digits above zero
elsewhere. While low-level cold advection is ongoing, a
persistent region of stratus across far northeast Illinois and
northwest Indiana is muting the temperature fall a bit. Based
on latest satellite and guidance trends, it does look like we`ll
largely lose this area of cloud cover through daybreak or so,
but the delayed scattering may result in slightly "warmer"
temperatures in spots. Regardless, a steady northwesterly breeze
around 15 mph will result in morning wind chills in the 20 to
25 below range northwest of about I-55 and in the 15 to 20 below
range elsewhere (NW Indiana in particular). No changes planned
to the current Cold Weather Advisory.

Quiet but cold conditions are expected today as shortwave
ridging briefly builds in overhead. A fast-moving and intense
clipper system will push across the Upper Great Lakes tonight
and Tuesday morning. Mid-level heights falls on the order of 120
meters/12 hours are forecast to spread across parts of northern
Wisconsin and lower Michigan, highlighting the robust nature of
large scale forcing accompanying this system. A significant
layer of dry air is forecast to be in place across the local
region, however, which should generally limit the snowfall
threat across our area. That said, forecast soundings reveal
effective saturation occurring down to around or under 850 mb
late tonight during a brief window across the northeast half of
the CWA, and the latest GFS is now cranking out a little QPF
north and east of I-90. Given the intense forcing, have elected
to introduce a slight chance for snow late tonight/early Tuesday
morning in this region. The window for any snow will likely be
brief (2-3 hours or less), and it`s still possible dry air wins
out, but did not feel comfortable with a completely precip-free
forecast given the dynamics at play.

Increasing warm advection in advance of this system will
facilitate a gradual uptick in southwesterly winds this evening
and overnight. This in turn will eventually result in steady to
slowly-rising temperatures overnight. Prior to this, air
temperatures could briefly fall back into the negative single
digits in spots this evening, particularly across our far
southeast locales closer to the deeper snow pack which, when
combined with the increasing winds, may result in wind chills
briefly as cold as 20 below. Given the currently-expected brief
nature of these wind chills, did not issue another cold headline
given the anticipated "warming" overnight and through daybreak
Tuesday. With the increasing winds, some patchy blowing snow may
occur in open/rural areas within the deeper snowpack. It`s possible
that things have started to crust over a bit by tonight, but
did add some patchy blowing snow (probably will be more like low
drifting) wording to the grids for areas south of the Kankakee
River where reports of 3 to 4 inches were commonplace from
yesterday`s system.

A reinforcing cold front will sweep through the area during the
morning on Tuesday. Increasing cold advection may mute the
diurnal temperature rise, and it`s possible our current highs
are a smidge too warm depending on the magnitude of cold
advection. Increasing 0-1 km lapse rates should result in an
expansion of low stratus through the morning and into the
afternoon. Did contemplate adding some chances for snow showers,
but have held off for now given the still marginal-looking
nature to progged boundary layer moisture, which looks better
across southern Wisconsin. Noting that the recent ECMWF is
depicting some NW-SE oriented streaks of light QPF into the
region during this timeframe, so something to consider in future
forecast issuances given significant DCVA overhead.

On Wednesday, the next disturbance is slated to press across the
region. The trend over the last few model cycles has been
towards a bit of a drier and farther south outcome, with less
modeled precip. Still somewhat skeptical of a completely dry
outcome given the upper jet forcing and degree of mid-level
saturation, but given the very limited signal across the
ensemble suite, have left the NBM-delivered dry conditions as
is.

Beyond this, the signal for an expansive upper trough cutting
south and westward across the Great Lakes continues to grow in
the guidance suite towards the end of the week. With this
occurring as another 1050s mb arctic high builds southward
across the north-central CONUS, the potential for another round
of lake effect snow is evident from about Thursday night
through Saturday. With ice cover likely to expand with time,
it`s a bit unclear how this might impact surface fluxes,
although latest GLERL ice forecasts indicate ice coverage likely
won`t extend beyond 15-20 miles, with a wide open fetch
available along the long axis of the lake. With the colder lake
temperatures, thermodynamics are not off the charts, but
certainly more than sufficient for intense lake effect with
surface-850 delta Ts near 20 C and lake-induced ELs just under
9-10 kft. Way too much uncertainty at this time range to make
any adjustments to the blended slight chance PoPs, but this will
be a period to keep a close eye on.

Carlaw

&&

.AVIATION /06Z TAFS THROUGH 12Z TUESDAY/...
Issued at 1059 PM CST Sun Jan 25 2026

Various VFR stratus decks based near 5kft and 8kft will ebb and
flow over the airspace through the overnight hours, perhaps
lasting longest at Lake Michigan-adjascent terminals. An
occasional flurry or two may occur beneath either deck as well,
particularly near ORD/MDW. Winds will remain out of the
northwest through the overnight hours with a gust up to 20 kt or
so from time to time.

As a surface high pressure system slides southeastward from the
northern Plains to the Lower Mississippi River Valley today,
the low-level pressure field across the Lower Great Lakes will
gradually reorient to enforce winds shifting toward the west and
eventually southwest. A gust or two to 20kt may occur during
the afternoon hours. Largely sunny skies are expected during
daylight hours, though a few stratocu clouds based near 1.5kft
may develop over the new snowpack near ORD/MDW/GYY.

After sunset, southwesterly winds will increase in magnitude as
the pressure gradient tightens ahead of a clipper system racing
into the Upper Great Lakes. A period of LLWS is expected
between 03- 09Z as southwesterly flow at 2kft increases to
50-55kt. A cold front with an associated west/northwesterly wind
shift will race across the airspace during the early morning
hours of Tuesday, perhaps accompanied by a snowflake or two.

Borchardt

&&

.HYDROLOGY...
Issued at 230 PM CST Fri Jan 23 2026

River gauges, reports from local officials, and reports from
trained ice spotters continue to indicate a few ice jams across
the area due to the significant increase in river ice over
recent days. With continued cold weather into next week,
conditions will remain favorable for river ice formation. While
no widespread flooding is expected, localized ice jams may
occur.

- NWS Chicago

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Cold Weather Advisory until noon CST today for ILZ003-ILZ004-
     ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-ILZ013-ILZ019-
     ILZ020-ILZ021-ILZ023-ILZ032-ILZ033-ILZ039-ILZ103-ILZ104-
     ILZ105-ILZ106-ILZ107-ILZ108.

IN...Cold Weather Advisory until noon CST /1 PM EST/ today for
     INZ001-INZ002-INZ010-INZ011-INZ019.

LM...Small Craft Advisory until 6 PM CST Tuesday for the IL and IN
     nearshore waters.

&&

$$

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